Process for the hydrocarboxylation of ethylenically unsaturated carboxylic acids

ABSTRACT

A process for the hydrocarboxylation of an ethylenically unsaturated carboxylic acid, by reacting it with carbon monoxide and a co-reactant selected from the group of water and carboxylic acids in the presence of a catalyst system including: (a) a source of palladium; (b) a bidentate diphosphine of formula (I), R 1 R 2 &gt;P—R 3 —R—R 4 —P&lt;R 5 R 6  (I) wherein P represents a phosphorus atom; R 1 , R 2 , R 5  and R 6  independently represent the same or different optionally substituted organic groups containing a tertiary carbon atom through which the group is linked to the phosphorus atom; R 3  and R 4  independently represent optionally substituted alkylene groups and R represents an optionally substituted aromatic group; (c) a source of anions derived from an acid having a pKa of less than 3, as measured at 18° C. in an aqueous solution.

PRIORITY CLAIM

The present application claims priority to European Patent ApplicationNo. 03076568.9 filed 22 May, 2003.

FIELD OF THE INVENTION

This invention relates to a process for the hydrocarboxylation of anethylenically unsaturated carboxylic acid.

BACKGROUND OF THE INVENTION

In WO2001/68583 there is disclosed a process for the carbonylation ofethylenically unsaturated compounds having 3 or more carbon atoms byreaction with carbon monoxide and an hydroxyl group containing compoundin the presence of a catalyst system including:

-   (a) a source of palladium;-   (b) a bidentate diphosphine of formula I,    R¹R²>P—R³—R—R⁴—P<R⁵R⁶  (I)    wherein P represents a phosphorus atom; R¹, R², R⁵ and R⁶    independently represent the same or different optionally substituted    organic groups containing a tertiary carbon atom through which the    group is linked to the phosphorus atom; R³ and R⁴ independently    represent optionally substituted alkylene groups and R represents an    optionally substituted aromatic group;-   (c) a source of anions derived from an acid having a pKa of less    than 3, as measured at 18° C. in an aqueous solution.

The process is carried out in the presence of an aprotic solvent. Thepreferred hydroxyl containing compounds according to WO2001/68583 arewater and alkanols. Notably, the hydrocarboxylation of unsaturatedcarboxylic acids is not mentioned in this document.

SUMMARY OF THE INVENTION

It has now been found that a process for the hydrocarboxylation of anethylenically unsaturated carboxylic acid with carbon monoxide and aco-reactant selected from the group of water and carboxylic acids can bevery effectively performed in the presence of a catalytic system whichdiffers from that described in WO2001/68583 in that the presence of aseparate solvent is only optional. The source of anions is not limitedto one having a pKa of less than 3.

Accordingly the present invention provides a process for thehydrocarboxylation of an ethylenically unsaturated carboxylic acid byreacting it with carbon monoxide and a co-reactant selected from thegroup consisting of water and carboxylic acids, in the presence of acatalyst system which comprises:

-   (a) a source of palladium;-   (b) a bidentate diphosphine of formula I,    R¹R²>P—R³—R—R⁴—P<R⁵R⁶  (I)    wherein P represents a phosphorus atom; R¹, R², R⁵ and R⁶    independently represent the same or different optionally substituted    organic groups containing a tertiary carbon atom through which the    group is linked to the phosphorus atom; R³ and R⁴ independently    represent optionally substituted alkylene groups and R represents an    optionally substituted aromatic group; and-   (c) a source of anions derived from an acid.

DETAILED DESCRIPTION OF THE INVENTION

In the process according to the invention, suitable sources forpalladium of component (a) include palladium metal and complexes andcompounds thereof, such as palladium salts, for example the salts ofpalladium and halide acids, nitric acid, sulphuric acid or sulphonicacids; palladium complexes, e.g. with carbon monoxide oracetylacetonate, or palladium combined with a solid material such as anion exchanger. Preferably, a salt of palladium and a carboxylic acid isused, suitably a carboxylic acid with up to 12 carbon atoms, such assalts of acetic acid, propionic acid and butanoic acid, or salts ofsubstituted carboxylic acids such as trichloroacetic acid andtrifluoroacetic acid. A very suitable source is palladium(II) acetate.

In the diphosphine of formula I, R represents an optionally substitutedaromatic group which is linked to the phosphorus atoms via the alkylenegroups. The aromatic group can be a monocyclic group, such as forexample a phenyl group or a polycyclic group, such as for examplenaphthyl, anthryl or indyl group. Preferably, the aromatic group Rcontains only carbon atoms, but R can also represent an aromatic groupwherein a carbon chain is interrupted by one or more hetero atoms, suchas nitrogen, sulphur or oxygen atom in for example a pyridine, pyrrole,furan, thiophene, oxazole or thiazole group. Most preferably thearomatic group R represents a phenyl group.

Optionally the aromatic group is substituted. Suitable substituentsinclude groups containing heteroatoms such as halides, sulphur,phosphorus, oxygen and nitrogen. Examples of such groups includechloride, bromide, iodide and groups of the general formula —O—H, —O—X²,—CO—X², —CO—O—X², —S—H, —S—X², —CO—S—X², —NH₂, —NHX², —NR²X³, —NO₂, —CN, —CO—NH₂, —CO—NHX², —CO—NX²X³ and —CI₃, in which X² and X³,independently, represent alkyl groups having from 1 to 4 carbon atomslike methyl, ethyl, propyl, isopropyl and n-butyl. When the aromaticgroup is substituted it is preferably substituted with one or more aryl,alkyl or cycloalkyl groups, preferably having from 1 to 10 carbon atoms.Suitable groups include, methyl, ethyl, propyl, iso-propyl, butyl andiso-butyl, phenyl and cyclohexyl.

Most preferably, however, the aromatic group is non-substituted and onlylinked to the alkylene groups which connect it with the phosphorusatoms. Preferably the alkylene groups are connected at adjacentpositions, for example the 1 and 2 positions, of the aromatic group.

Preferably the alkylene groups are lower alkylene groups. By loweralkylene groups is understood alkylene groups comprising from 1 to 4carbon atoms. The alkylene groups can be substituted, for example withalkyl groups, or non-substituted. Preferably the alkylene groups arenon-substituted. More preferably the alkylene groups are unsubstitutedmethylene or ethylene groups, most preferably methylene groups.

R¹, R², R⁵ and R⁶ can independently represent organic groups containinga tertiary carbon atom through which the group is linked to thephosphorus atom. The groups R¹, R², R⁵ and R⁶ are only connected to eachother via the phosphorus atom. The organic groups preferably have from 4to 30 carbon atoms, yet more preferably from 4 to 20 carbon atoms, andagain more preferably from 4 to 8 carbon atoms. The tertiary carbon atomcan be substituted with aliphatic, cyclo-aliphatic or aromaticsubstituents or can form part of a substituted saturated ornon-saturated aliphatic ring structure. Hence examples of suitableorganic groups are tert-butyl, 2-(2-methyl)-butyl, 2-(2-ethyl)butyl,2-(2-phenyl)butyl, 2-(2-methyl)pentyl, 2-(2-ethyl)pentyl,2-(2-methyl-4-phenyl)-pentyl, 1-(1-methyl)cyclohexyl and 1-adamantylgroups, and derivatives of these groups, wherein one or more of thecarbon atoms are substituted by heteroatoms. Again preferably, thetertiary carbon atom is substituted with alkyl groups, i.e. preferablythe organic group is a tertiary alkyl group. Of these, tert-butyl groupsand 1-adamantyl groups are most preferred. Preferably the groups R¹, R²,R⁵ and R⁶ represent the same tertiary alkyl groups, most preferablygroups R¹, R², R⁵ and R⁶ are tert-butyl groups.

An especially preferred bidentate diphosphine is1,2-bis[(di(tert-butyl)phosphinomethyl]benzene (also known asbis[di(tert-butyl)phosphino]-o-xylene).

The ratio of moles of bidentate diphosphine, i.e. catalyst component(b), per mole atom of palladium, i.e. catalyst component (a), rangesfrom 0.5 to 20, preferably from 1 to 10.

Examples of suitable anions, i.e. component (c) of the catalyst system,include anions of phosphoric acid, sulphuric acid, sulphonic acids,carboxylic acids and halogenated carboxylic acids such astrifluoroacetic acid.

Sulphonic acids are in particular preferred, for exampletrifluoromethanesulphonic acid, p-toluene-sulphonic acid and2,4,6-trimethylbenzene sulphonic acid, 2-hydroxypropane-2-sulphonicacid, tert-butyl sulphonic acid and methyl sulphonic acid. Especiallypreferred sulphonic acids are methyl sulphonic acid, tert-butylsulphonic acid, 2,4,6-trimethylbenzene sulphonic acid. Yet morepreferred anions are anions of acids having a pKa of above 3, such ascarboxylic acids.

Suitable carboxylic acids are those having from 2-20 carbon atoms, suchas acetic acid, propionic acid butyric acid, pentanoic acid and nonanoicacid. Very conveniently the acid corresponding to the unsaturatedcarboxylic acid reactant can be used as catalyst component (c). In casethe reactant is 3-pentenoic acid, this same acid can be convenientlyused as the catalyst component (c) as well. The carboxylic acid may alsobe a mixture of the reactant and its structural isomers. In the case thereactant is 3-pentenoic acid, these include the 2- and 4-pentenoic acidother than the cis-3-pentenoic acid and/or trans-3-pentenoic acid.

Catalyst component (c) can also be an ion exchanging resin containingsulphonic acid groups or carboxylic acid groups.

The molar ratio of the source of anions and palladium, i.e. catalystcomponents (c) and (b), is suitably between 2:1 and 10⁶:1 and morepreferably between 2:1 and 10⁵:1.

The process may optionally be carried out in the presence of a solvent.

The ethylenically unsaturated carboxylic acid has at least 3 carbonatoms. Preferably the ethylenically unsaturated carboxylic acid has from4 to 20 and more preferably from 4 to 14 carbon atoms, such as acrylicacid, 2-cis-pentenoic acid and/or 2-trans-pentenoic acid or a mixturethereof, 3-cis pentenoic acid and/or 3-trans-pentenoic acid or a mixturethereof 3-pentenoic acid, 4-pentenoic acid, undecenoic acid,cyclopentene carboxylic acid, dicyclopentene carboxylic acid andcyclohexene carboxylic acid. The ethylenically unsaturated carboxylicacid can be substituted or non-substituted.

The co-reactant is water, a carboxylic acid or a combination thereof.Inasmuch as the co-reactant is water, the product obtained will bedibasic carboxylic acid. Mono anhydric carboxylic acids are obtainedinasmuch as the co-reactant is a carboxylic acid. Preferably thecarboxylic acid co-reactant has the same number of carbon atoms as theethylenically unsaturated carboxylic acid reactant.

The ratio (v/v) of ethylenically unsaturated carboxylic acid and watercan vary between wide limits and suitably lies in the range of 1:0.1 to1:10, more suitably from 2:1 to 1:2.

The hydrocarboxylation reaction according to the present invention iscarried out at moderate temperatures and pressures. Suitable reactiontemperatures are in the range of 50-250° C., preferably in the range of80-150° C. The reaction pressure is usually at least atmospheric.Suitable pressures are in the range of 0.1 to 15 MPa (1 to 150 bar),preferably in the range of 0.5 to 8.5 MPa (5 to 85 bar).

Carbon monoxide partial pressures in the range of 0.1 to 6.5 MPa (1-65bar) are preferred. In the process according to the present invention,the carbon monoxide can be used in its pure form or diluted with aninert gas such as nitrogen, carbon dioxide or noble gases such as argon.

In the process of the present invention, the addition of limited amountsof hydrogen, such as 3 to 20 mol % of the amount of carbon monoxideused, promotes the hydrocarbonylation reaction. The use of higheramounts of hydrogen, however, tends to cause the undesirablehydrogenation of the ethylenically unsaturated carboxylic acid reactant.

The amount of catalyst used in the process is not critical. Good resultsare obtained when the amount of palladium is in the range of 10⁻⁷ to10⁻¹ gram atom per mole of ethylenically unsaturated compound.Preferably this amount is in the range of 10⁻⁵ to 5×10⁻² gram atom permole.

The invention will be illustrated by the following examples.

EXAMPLES 1-3 Hydrocarboxylation of 3-pentenoic Acid to Adipic Acid

A 250 ml stirred autoclave, made of HASTELLOY C, was charged with 40 mldiglyme (diethylene glycol dimethyl ether), 5 ml water and 15 ml3-pentenoic acid (HASTELLOY C is a trademark). Then a solution of thepreformed catalyst composition of 0.1 mol palladium acetate, 0.5 mol ofthe ligand and 1 mol methane sulphonic acid in 10 ml of acetone wasadded and the autoclave was closed and evacuated.

The ligand in Examples 1-3 was1,2-bis[di(tert-butyl)phosphinomethyl]benzene and in

Comparative Example A it was 1,3-bis(di-tert-butylphosphino)propane.

The autoclave was pressurized with CO to 3 MPa and heated at 90 or 105°C. for 10 hr.

After reaction the autoclave was cooled and opened. The contentsconsisted of a slurry of adipic acid, diglyme and pentenoic acid.

The initial carbonylation rate (mol per mol Pd per hour) of this batchoperation, as presented in Table I, is defined for Examples 1-3 as themean rate of carbon monoxide consumption (pressure drop) over the first30% substrate consumption. For Comparative Example A, which did notreach 40% substrate consumption, the initial carbonylation rate isdefined as the mean rate of CO consumption over the first two hours.

TABLE I Temp. Rate Example ° C. mol/mol Pd/hr 1 105 270 2 90 330 3 105330 A 100 10

The liquid phase of the slurry of Examples 2 and 3 was analysed withGlC, and showed a pentenoic acid conversion to adipic acid of more than90 mol % in both cases. Also, 15 g and 17 g respectively of white adipicacid was recovered by filtration at room temperature. Analysis by ¹H NMRin d-DMSO showed more than 99% purity of adipic acid in both cases.

The slurry of Comparative Example A was analysed in the same way andshowed a pentenoic acid conversion of 5 mol % and a purity of 60% adipicacid.

EXAMPLES 4-7 Hydrocarboxylation of 3-pentenoic Acid Out of a Mixture toAdipic Acid

A mixed substrate of the following composition was used:

butenyl esters of pentenoic acid 6.1 wt % butenyl esters of nonanoicacid 1.4 wt % cis/trans 3-pentenoic acid 84.0 wt %  2- and 4-pentenoicacid 1.4 wt % nonanoic acid 6.9 wt %

Four batches of 30 ml each of this mixed substrate were reacted with COand water as follows.

A 250 ml magnetically stirred autoclave, made of HASTELLOY C, wascharged with water as specified in Table II below and with 30 ml of thedistilled product of Example 13. Then 0.1 mol palladium acetate and 0.5mol of the ligand 1,2-Bis(di-tert-butylphosphinomethyl)benzene wereadded and the autoclave closed and evacuated. The autoclave waspressurized with H₂ and/or CO to partial pressures as indicated in TableIII, sealed, heated to 135° C. and maintained at that temperature for 15hours. Finally the autoclave was cooled and the reaction mixture wasanalysed with GLC.

The reaction mixture was almost completely composed of solid adipicacid. THF was added to form a slurry of adipic acid in THF. The THFphase was analysed by GLC and the conversion of pentenoic acid wasdetermined from the residual pentenoic acid. In all experimentspentenoic acid conversion was higher than 90%. Selectivity to adipicacid was >95%.

The initial carbonylation rate (mol per mol of Pd per hour) of thisbatch operation, as presented in Table II, is defined as the mean rateof carbon monoxide consumption (pressure drop) over the first 30%substrate consumption.

TABLE II H₂ Initial Induction partial CO partial carbonylation Watertime pressure pressure rate mol/mol Example charge (hr)** MPa MPa Pd/hr4 5 ml 6 10 40 610 5 5 ml 5 — 60 700 6 7 ml 10 — 65 730 7 2 + 5 ml* <1 —65 880 *5 ml were added after 1 hr reaction **The induction time iscaused by the butenyl pentenoic acid esters present in the feed (6.1 wt% according to Table II), which here were initially converted topentenoic acid and butadiene. At the low initial water concentration ofExample 7 this pentenoate conversion was rapidly achieved.

1. A process for the hydrocarboxylation of an ethylenically unsaturatedcarboxylic acid by reacting it with carbon monoxide and a co-reactantselected from the group consisting of water and carboxylic acids in thepresence of a catalyst system which consists of: (a) a source ofpalladium; (b) a bidentate diphosphine of formula I,R¹R²>P—R³—R—R⁴—P<R⁵R⁶  (I) wherein P represents a phosphorus atom; R¹,R², R⁵ and R⁶ independently represent the same or different optionallysubstituted organic groups containing a tertiary carbon atom throughwhich the group is linked to the phosphorus atom; R³ and R⁴independently represent optionally substituted alkylene groups and Rrepresents an optionally substituted aromatic group; and (c) a source ofanions derived from an acid having a pKa of above
 3. 2. The process ofclaim 1 wherein R is a phenyl group.
 3. The process of claim 1 whereinR³ and R⁴ are methylene groups.
 4. The process of claim 1 wherein R¹,R², R⁵ and R⁶ are tert-butyl groups.
 5. The process of claim 1 whereinthe source of anions is derived from the acid corresponding to theunsaturated acid carboxylic acid reactant.
 6. The process of claim 1wherein the source of anions is derived from a carboxylic acid.
 7. Theprocess of claim 1 wherein the reaction temperature is in the range of50° C. to 250° C., the reaction pressure is in the range of 0.1 to 15MPa, and the carbon monoxide partial pressure is in the range of 0.1 to6.5 MPa.
 8. The process of claims 1 wherein an amount of 3 to 20 mol %,related to the carbon monoxide, of hydrogen is added.
 9. The process ofclaims 1 wherein the ethylenically unsaturated carboxylic acid has from4 to 20 carbon atoms.
 10. The process of claim 9 wherein theethylenically unsaturated carboxylic acid is pentenoic acid.
 11. Theprocess of claim 1 wherein the source of anions is an ion exchangingresin containing carboxylic acid groups.